Punch press ram structure



Jan- 31, 1967 H. PETERsoN PUNCH PRESS RAM STRUCTURE Filed OCb. 22, 1965 l/VVE/VTOR BV H L. PETERSON ATTORNEY United States Patent O This invention relates to punch presses, and more particularly, the die holding devices for punch presses that are used for relatively small-lot punchings.

Punch presses that are used for piercing operations typically include a rarn for forcing a punch member in v an upper die plate against a workpiece that is mounted on a lower die plate. A stripper bar that is stationary with respect to the ram and which intercepts the workpiece after the punching operation is usually used'to dislodge the workpiece from the punch member as the ram is rel tracted to its initial position. The upper die member typically includes a pair of guide pins or pilot pins adapted to protrude through apertures in the lower die member for ensuring the requisite alignment of the two die members during repeated punching operations. While conventional punch presses are quite satisfactory for permanent use, they are relatively inefficient for smalllot punching operations because of the difficulty of changing and replacing the upper die plate. A rather complicated dismantling operation is required for removing and replacing the upper die plate.

Attempts at simplfying the die interchanging operation have generally created other problems. A major obstacle to the design o-f a simple die holder in the ram is the stationary stripper bar. By redesigning the punch press so that the punching or piercing member is onthe lower die holder, the stripper bar can be eliminated. In this case, the stripping operation is accomplished by pneumatic apparatus in the base of the press which forces a piston upwardly against the workpiece to dislodge it from the punch member. It can be appreciated that such modification requires a complete redesigning of the pun-ch press and in many cases makes retrieval of the finished workpiece more difficult. For example, if the workpiece is stripped from a punch member in the ram, it can be caught in a catch tray, while catch tray retrieval of the workpiece is impractical if the punching member is in the base.

Accordingly, it is an object of this invention to provide a punch press having a punch element in the upper die plate which is readily removable from the ram and which is readily replaceable.

These and other objects of my invention are attained in an illustrative embodiment thereof comprising a punch press of the general type described above in which the punch member is included in the upper die plate. The ram of the punch press comprises a ram enclosure dened by a top wall, a bottom wall and a pair of side walls, which is lopen at opposite ends. Extending along the bottom surface of the bottom wall of the ram enclosure are a pair of parallel die holders, each having a pair of steps. The upper die plate is Slidably mounted bet-Ween the uppermost steps of the two guide members and abuts firmly against the bottom surface of the bottom wall of the ram enclosure. Mounted between the lowermost steps `of the guide members is a stripper plate which does not normally abut against the upper die plate and which is therefore free to move vertically for abutment against the upper die plate. Extending downwardly through apertures in the stripper plate are a pair of guide pins `for aligning the upper die plate in a conventional manner ICC with the lower die plate. At least one punch member on the die plate protrudes into an aperture in the stripper plate. Slidably mounted in apertures in the bottom wall of the ram enclosure are a pair of stripper pins which eX- tend downwardly through apertures in the die plate to about against the stripper plate. Overlaying the stripper pins is a striking plate. A pair of hydraulic cylinders Slidably mounted within the ram enclosure include pistons which, in response to a signal, eXert a downward force on the striking plate and the stripper pins.

During the punching operation, the workpiece abuts against the stripper plate and forces it upwardly against the die plate which causes the punch member to protrude through the stripper plate and -through the workpiece to perform the ydesired piercing operation. As the ram is retracted, the workpiece adheres to the punch member. In response to a signal, the hydraulic cylinders force the striking plate and slidable stripper pins downwardly through apertures in the die plate against the stripper plate. The downward force of the stripper plate dislodges the workpiece and the stripper plate descends to its original position on the lowermost steps of the parallel 1die holders.

The hydraulic cylinders are mounted on a mounting plate which in turn are mounted within parallel grooves in opposite side walls of the ram enclosure. Manually operable locking pins maintain the cylinders in their proper position during operation. When the upper die plate is to be replaced, the locking pins are released and the hydraulic cylinders are removed from the ram enclosure by sliding them out through the open ends. With the cylinders removed, the st-ripper pins can be manually removed from the bottom wall of the ram enclosure which, in turn, permits the die plate and stripper plate to be removed simply by sliding them as a unit out through the guide members.

When compared with prior punch presses, it can be appreciated that my punch press loffers substantial advantages 0f convenience in replacing the upper die member. Replacement of the die member does not require any massive nuts to be loosened with a wrench as is normally the case; the only securing elements to be operated are the simple locking pins which will be described in more detail later. The hydraulic cylinders which I will describe later, are of light weight and easily remove-d from the ram enclosure. Replacement lof the die mem ber is easily accomplished simply by sliding the upper die member along the parallel die holder steps, inserting the stripper pins, the striking plate, the hydraulic cylinders, and operating the lock pins.

These and other objects, advantages, and features of my invention will be better appreciated from a consideration of the following detailed description, taken in conjunction with the accompanying drawing in which:

FIG. lpis a perspective view of part of a punch press in accordance `with the invention;

FIG. 2 is a side view of part of the apparatus of FIG. 1; and

FIG. 3 is a side view of part of the apparatus of FIG. 1 illustrating the punching operation of the punch press.

Referring now to FIGS. l and 2, there is shown a punch press comprising a ram 10 and a base 11. The ram includes a ram enclosure 12 having an upper wall I13, a lower wall 14, and two side walls 15 and 16. Extending along the bottom surface of the bottom wall 14 are a pair of die holders 17, best shown in FIG. 2. Mounted between the die holders 17 is a punching element 18 the purpose of which is to pierce a workpiece 19. The workpiece is mounted on a lower die plate 20 which in turn is mounted between a pair of parallel guide members 21 shown in FIG. l. The lower die plate 20 preferably reci-procates back and forth along `guide members 21 so that a new workpiece 19 can 'be replaced after each punching operation.

As shown in FIG. 2, facing surfaces of the die holders 17 have a staircase shape to dene an upper step 22 and a lower step 23. Mounted `between the upper steps 22 is an upper die plate 24 which contains the punching element 18. Slidably mounted between the lower steps 23 is a stripper plate 25. The punching element 18 extends into an aperture in the stripper plate 25 but does not protrude through the stripper plate. A pair of guide pins 26 extend downwardly through apertures in the die plate 24 and the stripper plate 25, their purpose being to accurately align the upper and lower dies during each successive punching operation by protruding into alignment apertures 27 in the lower die plate 20. The guide pins 26 each have enlarged head portions which are free to slide in grooves in the lower surface of the bottom wall 14. Slidably mounted within apertures in the bottom wall 14 are a pair of stripper pins 29 which abut against the stripper plate 25. Resting on the bottom wall of the enclosure 12 and on the stripper pins is a striking plate 30.

Also mounted within enclosure l12 are two pairs of hydraulic cylinders 31. Each pair is mounted on a mounting plate 32 which in turn are mounted within parallel facing grooves 33 in side walls 15 and 16. As is shown more clearly in FIG. 1, the hydraulic cylinders can be removed by sliding them out through either of two open ends of the enclosure 12; for illustrative purposes, one pair of the cylinders of FIG. l are shown as having been removed. As shown in FIG. 1, each of the mounting plates 32 has a notch or slot 35 on one side. A pair of cavities 36 in side wall 16 are located at positions corresponding to the slots 35. Extending into these cavities are lock pins 37 which are biased against the notches 35 by springs 39. Hence, when the mounting plates 32 are properly located within the enclosure 12, the lock pins 37 are forced within the slots 35 to keep the hydraulic cylinders from sliding tout of position.

Included on the lock pin 37 is a retainer pin 40, best shown in FIG. 1. When the hydraulic cylinders are to be removed from the enclosure, lock pin 37 is pulled away from the slot 35 and is turned 90 degrees so that retainer pin 40 abuts against side wall 16 to hold the lock pin within the cavity 36 of the side wall and out of Contact with the mounting plate 32. With the lock pin 37 in this position, the mounting plate is free to slide out of the enclosure as shown in FIG. 1.

The hydraulic cylinders 31 may be model 2600 cylinders, commercially available from the Power Lock Company. This particular model is of suiciently light weight to be installed in a ram enclosure of a conventional punch press as shown in FIG. l. Hydraulic fluid is fed to the cylinders by hoses 42 which are of sufficient thickness to support by themselves the cylinder 31 and mounting plate 32 when they are removed from the enclosure. As is known, actuation of the cylinders 31 by a signal source (not shown) causes a piston within each cylinder to be forcibly projected downwardly from the cylinder, as will be explained more fully later.

The punching operation of the punch press is illustrated in FIG. 3. When the ram is forced downwardly against the workpiece 19, the stripper plate 25 is forced upwardly to abut on the die plate 24. As a result, the punching element 18 protrudes through the aperture of the stripper plate 25 and pierces the workpiece 19. A conventional die opening 43 in the lower die plate 20 permits the punching element 1S to pierce completely the workpiece 19. A piece of punch scrap 44 is shown droppin-g from the die aperture 43. The guide pins 26 protr-ude through alignment apertures in the lower die plate to ensure alignment of the punching element 18 with the aperture 43. Movement of the stripper plate forces stripper pins 29 upwardly and forces striking plate 30 against the hydraulic cylinders 31.

As the ram withdraws to its initial position, an approipriate signal actuates hydraulic cylinders 31 to project pistons 45 forcibly downwardly. The pistons 45, acting through striking plate 30 and stripper pins 29, force the stripper plate 25 back to its initial position 'between opposite steps 23. This dis-lodges the impaled workpiece from punching element 18. The detached workpiece may =be retrieved :by a catch tray or any other suitable apparatus.

The main advantage of the apparatus shown and described is that the die members can be quickly and conveniently removed and replaced. It is clear that the lower die member 20 can be replaced by simply sliding it out through the lguide members 21. The upper die member 24 can be replaced `by pulling the lock pins 37 out of engagement with mounting plate 32 and sliding the four hydraulic cylinders out through the open ends of the ram enclosure. Referring to FIG. 2, the striking plate 30 can then be removed and the stripper pins 29 removed frorn their apertures in the bottom wall 14. With the stripper pins 29 removed, the die plate 24, stripper plate 25, and guide pins 26 are free to slide as a unit between holders 17 and thereby be removed. Replacement is etfected by the reverse operation; die plate 24 and stripper plate 25 are guided into position between holders 17, stripper pins 29 are inserted through apertures in the -bott-om wall, striking plate 30` is replaced, hydraulic cylinders 31 are guided into position by grooves 33 and lock pins 37 are rotated to apply a spring bias against the slots 35 of the mounting plates 32.

From the foregoing it can be appreciated that my punch press apparatus is particularly advantageous for small-lot punching operations in which the die members are frequently replaced. No bolting or unbolting is required during replacement and little trouble or inconvenience is required -for ensuring proper alignment. These advantages result in large part from my use of hydraulic cylinders as the stripper mechanism which are integral with and movable with, the ram. This feature together with the various slidable mounts, the manually operable lock pins, the slidable and removable stripper pins and guide pins which aid in holding the die plate and stripper plate assembly in their proper locations, combine to give the advantage of a simple structure and convenient die replacement.

The embodiment shown and described is intended to be merely illustrative of the inventive concept. Various other embodiments and modications may be made by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. In a punch press, the combination comprising:

a vertically movable ram comprising an enclosure having a top wall, two side walls, a bottom wall, and two open ends;

a pair of parallel facing die holders extending along a bottom surface of the bottom wall;

said die holders each defining an upper step and a -lower step;

a die plate mounted on the upper steps of the holders and being horizontally slidable;

a stripper plate mounted on the lower steps of the holders and being slidable in the horizontal and vertical directions;

a punch member extending downwardly from the die plate through an aperture in the stripper plate;

a plurality of stripper pins vertically slidably mounted in apertures in the bottom wall of the ram enclosure and extending downwardly through apertures in the die plate;

means comprising at least one hydraulic cylinder for exerting a downward force on the stripper pins in response to a signal;

said hydraulic cylinders being mounted within the enclosure on a plate that is Slidably contained within horizontal grooves :on the two side walls, whereby the die plate can be removed by sliding the hydraulic cylinder out one end of the enclosure, removing the `stripper pins from the apertures in the Ebottom wall, and sliding the die plate and stripper plate out throu-gh the die holders.

2. The combination `of claim l further comprising:

a lower die plate for mounting a workpiece below the ram;

a pair of guide apertures in the lower die plate;

a pair of guide pins each extending through apertures in the die plate, and the stripper plate, and being adapted to protrude through the apertures in the lower die plate;

a pair of grooves extending along the bottom surface of the bottom wall of the ram enclosure parallel with the die holders;

said guide pins having enlarged head portions adapted to iit into the grooves on the bottom surface of the bottom wall.

3. The combination of claim l wherein said hydraulic cylinder is mounted on a plate, and further comprising:

a pair of grooves extending along the inner surfaces of the side walls of the rarn enclosure;

`said mounting plate being slidably mounted within the grooves of the side Walls;

and a manually operable spring-biased lock for locking the mounting plate within the ram enclosure.

4. In a punch press, the combination comprising:

a movable ram for forcing a punch member into a workpiece;

said ram comprising a wall upon which is mounted a pair of parallel die holders;

a stripper plate -being slidably mounted between opposite steps of the holders;

a die plate being slidably mounted between other opposite steps of the die holders between the stripper plate and the wall;

the punch member extending from the die plate through an aperture in the stripper plate, ybut not substantially beyond the stripper plate;

a pair of stripper pins abutting at one end against the stripper plate and extending through apertures in the die plate and the wall;

said stripper plate being free to move in the direction of the die plate when forced against the workpiece, whereby the punch member may protrude through the stripper plate to pierce the workpiece;

and means contained within the ram for selectively forcing the stripper pins against the stripper plate, thereby stripping the workpiece away from the punch member;

said stripper pin forcing means `being laterally -rnovable and the die holders being unobstructed, whereby the die plate can be removed by removing the stripper pins from the apertures in the wall, and sliding the die plate and stripper plate out through the guide members.

5. The combination of claim 4 wherein:

the stripper pin forcing means is mounted on a mounting plate which in turn is slidably mounted within parallel grooves on opposite first and second inner side walls of the ram;

a discrete cavity in the first side wall intercepts a groove;

a notch in the plate is adapted to be oriented opposite the cavity;

a lock pin extends through the rst side wall in the cavity and is spring biased against the notched portion of the mounting plate;

the lock pin is manually axially movable against the spring bias, whereby the pin can be withdrawn into the cavity to per-mit the mounting plate to be removed by sliding it along the parallel grooves.

References Cited by the Examiner UNITED STATES PATENTS Re. 22,422 1/ 1944 Whistler et al. 83-164 2,244,613 6/1941 Freeman 83-136 X 2,379,003 6/1945 Hedberg 83-137 X 2,534,672 12/1950 Hedberg `83--137 WILLIAM W. DYER, IR., Primary Examiner.

JAMES M. MEISTER, Examiner. 

1. IN A PUNCH PRESS, THE COMBINATION COMPRISING: A VERTICALLY MOVABLE RAM COMPRISING AN ENCLOSURE HAVING A TOP WALL, TWO SIDE WALLS, A BOTTOM WALL, AND TWO OPEN ENDS; A PAIR OF PARALLEL FACING DIE HOLDERS EXTENDING ALONG A BOTTOM SURFACE OF THE BOTTOM WALL; SAID DIE HOLDERS EACH DEFINING AN UPPER STEP AND A LOWER STEP; A DIE PLATE MOUNTED ON THE UPPER STEPS OF THE HOLDERS AND BEING HORIZONTALLY SLIDABLE; A STRIPPER PLATE MOUNTED ON THE LOWER STEPS OF THE HOLDERS AND BEING SLIDABLE IN THE HORIZONTAL AND VERTICAL DIRECTIONS; A PUNCH MEMBER EXTENDING DOWNWARDLY FROM THE DIE PLATE THROUGH AN APERTURE IN THE STRIPPER PLATE; A PLURALITY OF STRIPPER PINS VERTICALLY SLIDABLY MOUNTED IN APERTURES IN THE BOTTOM WALL OF THE RAM ENCLOSURE AND EXTENDING DOWNWARDLY THROUGH APERTURES IN THE DIE PLATE; MEANS COMPRISING AT LEAST ONE HYDRAULIC CYLINDER FOR EXERTING A DOWNWARD FORCE ON THE STRIPPER PINS IN RESPONSE TO A SIGNAL; 